The present invention relates to fluid coupling devices, such as viscous drives, the fluid coupling devices being of the type that include both a fluid working chamber and a fluid reservoir chamber, and valving to control the quantity of fluid in the working chamber.
Although the present invention may be used advantageously in various configurations and applications, it is especially advantageous in a coupling device used to drive a radiator cooling fan of an internal combustion engine for an over-the-road truck, such as a Class 8 truck, and will be described in connection therewith.
Viscous drive clutch assemblies have become popular due to their ability to cycle repeat, engage at higher engine speeds, and have varying degrees of engagement. Viscous drives have an operating range of engagement, are generally less engaged at higher engine speeds and are generally more engaged at lower engine speeds.